Typically, absorbent articles comprise a liquid pervious material that faces the wearer's body, a liquid impervious material that faces the wearer's clothing, and an absorbent body or absorbent core that is sandwiched between the liquid pervious material and the liquid impervious material. In prior absorbent articles, a material comprising comminuted wood pulp, referred to as airfelt, was used in the absorbent core to absorb the liquids and other exudates deposited on the surface of the absorbent article. One of the disadvantages of using airfelt was that a thick layer of airfelt had to be used to obtain the needed capacity.
Recent attempts to improve the effectiveness of absorbent cores have included distributing particles of absorbent gelling material in the absorbent core. The absorbent capabilities of absorbent cores containing particles of absorbent gelling material are, however, often adversely affected by a phenomenon called "gel blocking". The term "gel blocking" describes a situation that occurs when a particle of absorbent gelling material is wetted and the particle swells. The swelling of a number of such particles inhibits liquid transmission into other portions of the absorbent core. Wetting of the rest of the absorbent core thereafter takes place via a very slow diffusion process. This may have the effect that the subsequent acquisition of liquid by the absorbent core becomes much slower than the discharge of the liquids to be absorbed. As a result, leakage from the absorbent article may take place well before the particles of absorbent gelling material in the absorbent core are fully saturated or before the liquid can diffuse or wick past the "blocking" particles into the rest of the absorbent core.
Another problem that exists in absorbent articles having absorbent cores comprised of airfelt, with or without absorbent gelling materials, is that such structures tend to collapse when the airfelt becomes wet. When the absorbent material collapses, it may wad up and become hard and inflexible. These problems can make the absorbent article very uncomfortable to wear and result in the loss in the ability of the absorbent article to process liquids as intended.
Wetting of the absorbent material can also cause any bonding between layers of absorbent material to lose their effectiveness and lead to the separation of such layers. In addition, any bonds between the absorbent material and the topsheet and backsheet of the absorbent article tend to lose their effectiveness when the absorbent material becomes wet. This can cause the absorbent material to become detached from the topsheet and backsheet, and to slump or slide down between the topsheet and backsheet. These problems are of particular concern in the case of diapers and brief-type incontinence garments. These garments are large in comparison to pad-type absorbent articles like sanitary napkins, and typically have absorbent material that both underlies the wearer's crotch and extends upward toward the wearer's waist. The absorbent material that extends upward toward the wearer's waist has a tendency to slump down as a result of its own liquid saturated weight when wetted.
The loss of the effectiveness of the bonds between the absorbent material and topsheet and backsheet can be observed by pulling a wet absorbent article apart. When a wetted absorbent article comprising cellulose or cellulose-based material is pulled apart, even if the cellulosic material was glued to the topsheet or backsheet, it can be observed that the majority of the cellulosic material will separate from the topsheet and backsheet leaving only a barely visible or microscopic layer of cellulosic fibers attached to the inside surfaces of the topsheet and backsheet. It is desirable to have such absorbent layers retain more of their prior to use integrity than this, and to have absorbent layers that remain more completely attached to the adjacent layers (such as the topsheet and backsheet) during use, and particularly when wetted.
In addition, the current trend is to make absorbent articles such as diapers increasingly thinner, softer, and more flexible. The thinness allows the diaper to fit the wearer's body more closely. It also allows groups of diapers to be fit into smaller, more convenient packages. For these reasons, thinner diapers are desired by many consumers.
A number of efforts have been directed toward providing improved absorbent articles and eliminating various of the above effects and/or other problems. Several patents discuss the addition of synthetic material to absorbent articles for various purposes. These include: U.S. Pat. No. 3,285,245 issued to Eldridge, et al.; U.S. Pat. No. 3,545,441 issued to Gravdahl; U.S. Pat. No. 3,976,074 issued to Fitzgerald, et al.; U.S. Pat. No. 4,047,531 issued to Karami; U.S. Pat. No. 4,054,141 issued to Schwaiger, et al.; U.S. Pat. Nos. 4,082,886 and 4,129,132 issued to Butterworth, et al.; U.S. Pat. No. 4,214,582 issued to Patel; and, U.S. Pat. No. 4,219,024 issued to Patience, et al. Other efforts are described in U.S. Pat. No. 4,610,678 issued to Weisman, et al. on Sep. 9, 1986; U.S. Pat. No. 4,673,402 issued to Weisman, et al. on Jun. 16, 1987; and European Patent Application EP-A-254,476 assigned to The Procter & Gamble Company, published Jan. 27, 1988, the disclosures of which are incorporated by reference herein. One attempt to solve the comfort problem is described in U.S. Pat. No. 4,397,644 issued to Matthews, et al. Despite these efforts, the search for improved absorbent articles has continued.
A need exists for absorbent articles with improved absorbent cores, especially those which have particles of absorbent gelling material therein. In particular, a need exists for absorbent articles with absorbent material that has a reduced tendency to collapse when wetted, and for absorbent articles that optimize the use of the core material therein. In addition, a need exists for absorbent articles which have absorbent material that remains attached to the adjacent component or layer (such as the topsheet and/or the backsheet) when the absorbent article is in its intended in-use configuration and has been wetted by bodily exudates. A need also exists to make absorbent articles such as diapers increasingly thinner, softer, and more flexible.
Therefore, it is an object of the present invention to provide absorbent articles having the characteristics described above.
These and other objects of the present invention will be more readily apparent when considered in reference to the following description and when taken in conjunction with the accompanying drawings.